Thyroidal regulation of substrate kinetics properties of cytochrome oxidase in rat liver mitochondria

Hiren R. Modi, Surendra S. Katyare, Samir P. Patel

Research output: Contribution to journalArticlepeer-review


Effects of thyroidectomy (Tx) and subsequent treatment with 3,5,3′-triiodothyronine (T3), and combined treatment (T R) with T3 + thyroxine (T4) on substrate kinetics properties of cytochrome oxidase of rat liver mitochondria were examined. Tx resulted in lowering of cytochromes content with decrease in the enzyme activity, and Km and Vmax. T 3 and TR regimens restored the cytochromes contents and the Vmax values to normal. In control, T3 and T R groups the enzyme activity resolved in two kinetic components; in Tx group three kinetic components were evident. The Km values for all components decreased significantly in the experimental groups with concomitant increase in catalytic efficiency, Kcat/K m. Significant alterations in the contents of total phospholipid and of cholesterol were noted while the changes in the phospholipids composition were only of restricted nature. Regression analysis revealed that total phospholipid, cholesterol and phosphatidylcholine, phosphatidylethanolamine play significant role in fine tuning the enzyme activity.

Original languageEnglish
Pages (from-to)272-278
Number of pages7
JournalIndian Journal of Clinical Biochemistry
Issue number3
StatePublished - 2008


  • Cytochrome oxidase
  • Kinetic properties
  • Liver mitochondria
  • Thyroid hormone
  • Thyroxine
  • Triiodothyronine

ASJC Scopus subject areas

  • Clinical Biochemistry


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